_Scyphia_ (Oken).--Mass cylindrical, simple, or branched, fistulous, ending in a large rounded pit, and composed entirely of a reticulated tissue. _Eudea_ (Lamouroux).--Mass filiform, attenuated, sub-pedicellate at one end, enlarged and rounded at the other, with a large terminal pit; surface reticulated by irregular lacunæ, minutely porous. _Halirrhoa_ (Lamouroux).--Mass turbinated, nearly regular, circular, or lobate; surface porous; a large central pit on the upper face. _Happalimus_ (Lamouroux).--Mass fungiform, pedicellate below, expanding conically, with a central pit above; surface porous and irregularly excavated. _Cnemidium_ (Goldfuss).--Mass turbinate, sessile, composed of close fibres and horizontal canals, diverging from the centre to the circumference; a central pit on the upper surface, cariose in the exterior and radiate at the margin. _Ierea_ (Lamouroux).--Mass ovoid, sub-pedicellate, finely porous; pierced on the upper part by many orifices, the terminations of the internal tubes. _Tethium_ (Lamarck).--Mass sub-globose, tuberose, composed of a cariose firm substance, strengthened by abundance of siliciary spicula, fasciculated, and diverging from the centre to the circumference. RHIZOPODA. Gervais and Van Beneden include under the name of _Rhizopods_, or _foot-rooted_ animals (so called from ριξα,, _root_; πους, ποδος, _footed animals_), those of the simplest organization, which may be characterised by the absence of distinct digestive cavities, and the presence of vibratile cilia, as well as by the soft parts of their tissues. This tissue emits prolongations or filaments which admit of easy extension, sometimes simple, sometimes branching. Occasionally we see these branching filaments withdraw themselves towards the mass of the body, disappear, and gradually melt into its substance in such a manner that the individual seems to absorb and devour itself. If, in exceptional cases, some of the superior animals, as the wolf, devour each other, the rhizopods go much farther: they devour themselves, so to speak! The rhizopods are found both in fresh and salt water. They live, as parasites, on the body of worms and other articulated animals. The class is divided into many orders. We shall speak here only of three, namely, the _Amoebæ_, _Foraminifera_, and _Noctiluca_. AMOEBÆ.